Computer graphics processing and selective visual display system – Computer graphics processing – Character generating
Reexamination Certificate
2000-03-23
2003-03-18
Bella, Matthew C. (Department: 2676)
Computer graphics processing and selective visual display system
Computer graphics processing
Character generating
C345S581000, C345S619000, C345S670000, C345S671000, C340S457100
Reexamination Certificate
active
06535214
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application is related to Japanese Patent Application No. HEI 11(1999)-086312 filed on Mar. 29, 1999, whose priority is claimed under 35 USC §119, the disclosure of which is incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device for display control, and more particularly to a semiconductor device for display control for generating bit-mapped display data to be given to a liquid crystal driving device for displaying characters, graphics and the like on a liquid crystal display.
2. Description of the Related Art
FIG. 15
is a block diagram showing the structure of a device necessary for displaying characters and the like according to the prior art.
In general, the above-mentioned device comprises a liquid crystal display
101
for displaying characters and the like, a liquid crystal driving device
102
for controlling the display of characters and the like, a ROM
104
for font data storage in which font data is stored for each character, a RAM
103
for temporary storage of font data in which font data to be displayed is temporarily stored and a CPU
105
.
An operation of displaying a character according to the prior art will be described below.
First of all, the CPU
105
operates to specify a character code to be displayed. In some cases, the character code is generated by a program processing or is prestored in a memory such as a RAM, a ROM or the like depending on the need. In general, the character code is defined for each character, and is defined as a shift JIS code or a JIS code in Japanese.
The CPU
105
utilizes special software to calculate a character storage address in the ROM
104
for font data storage in which font data corresponding to a specified character code is stored. In order to calculate the character storage address from the character code, a “character code-character storage address conversion table” shown in
FIGS. 23 and 24
is used. For example, while the smallest character code of the JIS code is “2120” in a hexadecimal number, the smallest address of the ROM
104
for font data storage is “0”. A corresponding relationship between the code and the address is described in the conversion table so that conversion from “2120” to “0” can be easily carried out.
FIG. 16
shows input and output terminals of the ROM
104
for font data storage. When addresses (A
0
to A
17
) are input to the input terminal, corresponding font data is output to output terminals (D
0
to D
15
).
FIG. 17
illustrates an example of the storage of font data of a 16-dot size character. A Chinese character (one element of Japanese writing system)
shown in a size of 16×16 dots.
FIGS. 23 and 24
show a character code-character storage address conversion table in the ROM
104
for font data storage illustrated in FIG.
16
.
The CPU
105
gives a calculated character storage address to the ROM
104
for font data storage. Then the CPU
105
reads font data output from the ROM
104
for font data storage and stores the font data in the RAM
103
for temporary storage of font data.
The CPU
105
repeats the above-mentioned processings to store all font data for one screen display on a liquid crystal screen in the RAM
103
for temporary storage of font data. Then, the CPU
105
transfers the data stored in the RAM
103
for temporary storage of font data to the liquid crystal driving device
102
, and gives a display position and the like on the liquid crystal display
101
. The liquid crystal driving device
102
to which these data are transferred carries out a processing of displaying the character of a character code transferred to the liquid crystal display
101
.
FIG. 20
shows a flowchart for the above-mentioned character display processing according to the prior art (S
101
to S
107
).
Japanese Unexamined Patent Publication No. HEI 4(1992)-294418 discloses a font pattern transfer LSI provided with a character generator wherein a character code is converted to a physical address of the character generator using an address conversion table ROM.
As described above, a character corresponding to a specified character code has conventionally been displayed. However, the font data stored in the ROM
104
for font data storage cannot be directly given to the liquid crystal driving device
102
depending on the combination of the input bus width of the liquid crystal driving device
102
and the size of the font data. Therefore, it has been necessary to carry out a processing of first expanding the font data stored in the ROM
104
for font data storage into the RAM
103
for temporary storage and then giving the expanded data to the liquid crystal driving device
102
. The CPU
105
has carried out almost all of a series of processings. The details of the processing will be described below.
FIG. 18
illustrates the storage of font data of a 12-dot size character in the ROM
104
for font data storage.
In the case where a character string to be displayed on the liquid crystal display
101
has two Chinese characters of
and
the character codes thereof are given with JIS codes of “3441” and “3B7A”, and with shift JIS codes of “8ABF” and “8E9A”.
The CPU
105
calculates the character storage address of the ROM
104
for font data storage from the character code by referring to the character code-character storage address conversion table shown in
FIG. 23
or FIG.
24
.
First, the first character of
of the character string will be mentioned.
FIG. 25
illustrates a relationship between a display RAM for the Chinese character of
provided in the liquid crystal driving device
102
and a screen display actually displayed on the liquid crystal display
101
.
As shown in
FIG. 25
, the relationship between the screen display of the liquid crystal display
101
and the contents of the display RAM provided in the liquid crystal driving device
102
assumes one-to-one correspondence. Thus, the data written into the display RAM is exactly displayed on the screen of the liquid crystal display
101
.
If input data have a width of 8 bits, one address of the display RAM provided in the liquid crystal driving device
102
has an 8-bit structure. For example, a write unit in an X direction is 8 bits and data having 8 bits is given to the display RAM to write actual data. Accordingly, if the data input width of the liquid crystal driving device
102
has 8 bits, the CPU
105
should input character data to the liquid crystal driving device
102
twice in the X direction and twelve times in the Y direction of the liquid crystal screen. As a result of the above character data input, the character of
is displayed on the liquid crystal screen as shown in FIG.
22
.
FIG. 19
illustrates an example of the storage of font data on the second Chinese character of
having a 12-dot size. In the case where the second character of
is to be displayed on the right side of the first character of
a space of five dots (a region “a” in
FIG. 26
) is formed between the two characters as shown in FIG.
26
.
More specifically, although the character data itself has a 12-dot size, an escapement width is restricted by the bit width or the like of the data input to the liquid crystal driving device
102
.
Conventionally, the character data has been once stored in the RAM
103
for temporary storage of font data to determine the escapement width irrespective of the data input width of the liquid crystal driving device
102
, and then the CPU
105
has carried out a processing of adjusting a bit position or the like in the RAM
103
for temporary storage as described above.
Moreover, the font data has been transferred to the liquid crystal driving device
102
not in a character unit but as pixel data (that is, data for each dot). In order to display a character on the liquid crystal display
101
, the CPU
105
needs to calculate a font data storage address from a given character code, give the calculated address to the ROM
104
for font data storage and transfer ch
Morikawa Yoshinao
Tanimoto Junichi
Bella Matthew C.
Birch & Stewart Kolasch & Birch, LLP
Rahmjoo Mike
Sharp Kabushiki Kaisha
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